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An innovative photocatalytic thin film nanocomposite (TFN) membrane was prepared and used for the simultaneous separation/degradation of methylene blue (MB) under UV irradiation. For this purpose, we used the sol-gel method to prepare the TiO2/MWCNTs nanophotocatalyst and added to the 1,3-phenylenediamine (MPD) solution during interfacial polymerization (IP) of 1,3,5-benzenetricarbonyl chloride (TMC) and 1,3-phenylenediamine monomers on the polysulfone (PSF) support. Using scanning electron microscopy (SEM) analysis and studying the cross-sectional images of membrane samples, it was revealed that the polyamide (PA) thin layer was well fabricated over the support membrane. The attendance of the TiO2/MWCNTs nanophotocatalyst in the PA thin layer of TFN samples was also proved using EDX (energy-dispersive X-ray) analysis. According to the results of the contact angle (CA), it is clear that the hydrophilicity of membrane samples first increased and then decreased by enhancing the TiO2/MWCNTs nanophotocatalyst content in the PA thin layer. In comparison with the pristine thin film composite (TFC) membrane, TFN samples showed higher water flux and MB removal when they were exposed to UV light. Finally, it turned out that the TFN membrane comprising 0.2 wt. % TiO2/MWCNTs nanophotocatalyst (TFN 0.2) had the foremost efficiency among TFNs with the water flux of 13 L/m2·hr and dye separation/degradation of almost 100% under UV irradiation.

In this research work, the Ti

Cellulose acetate (CA) microfiltration membranes were fabricated by a combined vapor-induced and wet phase separation technique. A systematic morphology study was performed on the membranes prepared under different fabrication conditions and dope solution compositions. The results showed that symmetric CA membranes could be obtained by controlling relative humidity, temperature and exposure time during vapor-induced phase separation step. While the surface morphology and pore size of the membranes could be mainly tailored by adjusting the dope solution composition. The performance study of the membranes showed that for operation at low transmembrane pressures, only symmetric membranes fabricated by vapor-induced phase separation process have permeability which can be reached 100 L/m2h using polyvinylpyrrolidone with an average molecular weight of 30,000 (PVPK30) or polyethylene glycol with an average molecular weight of 400 (PEG400) as additives. Bacteria removal performance of the membranes showed that samples prepared at optimized solution compositions of CA/PVP and CA/PEG fabricated at constant vapor-induced phase separation (VIPS) condition of 5 min exposure time, 45 °C and 55% relative humidity can completely filtrate the E. coli bacteria. The prepared CA membranes showed no cytotoxicity in mouse L929 fibroblast cells, confirming their biocompatible nature for possible water treatment or biomedical applications.

Recently, ultrathin two-dimensional (2D) materials, known as nanosheets, have attracted great interest owning to their ultimate structural and desirable physical, chemical, thermal, electrical, and optical characteristics. Various potential applications of 2D nanomaterials have been reported in electronics/optoelectronics, electrocatalysis, batteries, supercapacitors, solar cells, sensors, photocatalysis, and other environmental processes. Modification of polymeric membranes using nanosheets is increasingly reported in the literature. The incorporation of inorganic nanostructured additives, such as metal oxide and metal hydroxide nanosheets, can impart desired characteristics to the surface and matrix of the membrane and improves its filtration performance. This review summarizes the preparation methods of the metal oxide and metal hydroxide nanosheets, with a special emphasis on the recent advances in this field. The structural and physicochemical properties of the 2D nanosheets have been discussed, and after that, the applications of these nanosheets for modification of polymeric membranes are presented with a focus on the membranes used for environmental applications. Finally, the existing challenges and future perspectives for synthesis and membrane-related applications of 2D metal oxide and metal hydroxide nanosheets are discussed.

Contra-diffusion synthesis method was used to create a uniform layer of zeolitic imidazolate framework-8 (ZIF-8) on the porous polyvinylidene fluoride (PVDF) ultrafiltration membranes. SEM, FTIR, EDX, AFM and water contact angle analyses were used to characterize the prepared membranes. The modified membrane with 5 h contra-diffusion synthesis time showed maximum pure water flux of 134 L/m2 h nearly twice of that of the bare PVDF membrane (65.8 L/m2 h). The water purification performance of the prepared membranes was evaluated using dye removal efficiency and the ZIF-8 modified membranes exhibited better performance for dye removal due of the negatively charged surface.

Surface modification of a commercial polyamide nanofiltration membrane was achieved by UV induced graft polymerization of acrylic acid and incorporation of carboxylated-MWCNTs (COOH-MWCNTs). The grafting process was done under different monomer concentrations and UV exposure times. The modified membranes were characterized through scanning electron microscopy (SEM), atomic force microscopy (AFM), contact angle and zeta-potential analysis, and cross-flow filtration experiments. Changes in the surface hydrophilicity, negative charge and roughness of the modified membranes improved their permeability and fouling resistance significantly. The membrane grafted with 50 g/L acrylic acid under 5 min UV exposure showed the best filtration performance including pure water flux of 38.8 L/m2 h, salt rejections of 97.43% (Na2SO4) and 93.4% (NaCl), and flux recovery ratio (FRR) of 80.2% during bovine serum albumin (BSA) filtration. After optimizing grafting condition, different amounts of COOH-MWCNTs were dispersed in the monomer solution for embedding in the grafting layer. By adding 0.2 wt% COOH-MWCNTs to the grafting layer, a water flux improvement of around 30% was observed. But, excess loading of the COOH-MWCNTs led to compaction of the grafting layer and made it inflexible and subsequently, reduced the hydrophilicity and permeability of the membrane. Fouling tests with BSA aqueous solution showed that antifouling ability of the modified membranes was remarkably improved at all concentrations of the COOH-MWCNTs. Furthermore, salt rejection results displayed that simultaneous surface modification through grafting and COOH-MWCNTs embedding could effectively improve the nanofiltration performance of the membranes in the term of permeability, desalination and fouling resistance.

In this work, a nanocomposite of MoS2 nanosheets and oxidized multi-walled carbon nanotubes (O-MWCNTs) was prepared using the hydrothermal method. The successful synthesis of the MoS2/O-MWCNTs nanocomposite was further confirmed using a scanning electron microscope (SEM), energy dispersive X-Ray dot mapping, and X-ray diffraction analysis. The synthesized nanocomposite was used as a nanoadditive for the improvement of polyethersulfone (PES) polymeric membrane. The phase inversion route was used to prepare MoS2/O-MWCNTs blended membranes containing different amounts of nanocomposite (0–1 wt%). The morphology of the prepared membranes was studied using SEM and atomic force microscopy techniques. Asymmetric structure with small pores at the top layer and well-developed large finger-like pores and macro voids at the sublayer can be observed in fabricated membranes. The hydrophilicity enhancement of the PES membrane in the existence of nanocomposite was verified by the contact angle test. The modified membrane containing 0.75 wt% of MoS2/O-MWCNTs exhibited improved permeability of 64.1 L/m2 h bar, and high pollutants removal of 93.5% for reactive blue 19, 97.5% for rifampicin, 98.4% for reactive red 195, and 99% for bovine serum albumin, with enhanced flux recovery ratio of 60.8%. Moreover, the stability of the blended membrane in the long-time operation makes it a promising candidate to be applied in the treatment of textile and industrial wastewaters.

The present study offers an overview of the recent developments in the application and modification of PVC membranes, focusing on some applications such as water and wastewater treatment, ion exchange, gas separation, pervaporation, electromembrane extraction, and support of composite membranes. For this purpose, an introduction to different types of the PVC polymers is provided first, and then, the application of PVC in the membrane fabrication is discussed. Various PVC membranes with their preparation methods and applications are reviewed and a detailed study is done on the modification methods of the PVC membranes. A deep literature review is performed to report the basics for selecting an appropriate method and membrane fabrication system with required processing conditions to produce membranes with desired morphology, performance and stability. Finally, the commercial PVC membranes are overviewed and the challenges and future perspective of these membranes are discussed.

Thin film composite reverse osmosis (RO) membranes were fabricated by interfacial polymerization of m-phenylenediamine and trimesoyl chloride monomers and modified with amine-functionalized multi-walled carbon nanotubes (MWCNT-NH2), which dispersed in amine solution. The surface characteristics of the prepared membranes were studied by scanning electron microscopy (SEM), atomic force microscopy (AFM) and contact angle analysis. The desalination performance of the membranes was investigated in terms of water flux and NaCl rejection. The hydrophilicity and permeability of the modified membranes were increased without any reduction in their salt rejection. The fouling resistance of the membranes was evaluated by their flux decrement through filtration of bovine serum albumin (BSA) solution and water flux recovery ability after the fouling. The incorporating of MWCNT-NH2 into polyamide layer of RO membranes improved their fouling resistance by reducing surface roughness and increasing negative charge and hydrophilicity of the membrane surface. The membrane containing 0.002 wt% MWCNT-NH2 presented the best desalination and antifouling performance.

Polyamide reverse osmosis (RO) membrane was fabricated by interfacial polymerization of m-phenylenediamine and trimesoyl chloride and modified with natural clinoptilolite as a hydrophilic zeolite material embedded in the polyamide layer. The effect of glow discharge plasma treatment with different plasma gas pressures was investigated on the physical and chemical properties of the natural clinoptilolite and the resulted modified membranes. Scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) spectroscopy of the untreated and treated clinoptilolite confirmed the variation of its surface properties and formation of new Si OH Al bonds during the plasma treatment. The embedding of hydrophilic clinoptilolite in the polyamide layer decreased the roughness of membrane surface. Also, the water contact angle of the membranes showed the improved hydrophilicity of the modified membranes which was confirmed with the results of permeation tests. The membrane modified with 0.01 wt.% clinoptilolite treated under 1.0 Torr oxygen as the plasma gas showed the highest water flux improvement (39%) and fouling recovery ratio (88%) compared to the unmodified membrane.

Herein, we report the fabrication of carboxymethyl cellulose (CMC)/polyethersulfone (PES) thin-film composite nanofiltration membranes using a dip-coating method with glutaraldehyde (GA) as the crosslinking agent. The effects of crosslinking degree and the dip-coating parameters, including CMC concentration and dipping time, on the performance and morphology of the fabricated membranes were investigated. The properties of the prepared membranes were analyzed by ATR-FTIR, AFM, FE-SEM, and water contact angle analysis. The optimized membrane containing 0.2 wt% CMC, crosslinking degree of 20% by the dipping time of 10 min represented a rejection efficiency of 91.90%, 68.63%, and 45.90% towards the Na2SO4, MgSO4, and NaCl solutions (100 mg/L), respectively. The pure water flux of the optimal membrane was 47.90 ± 1.77 L/m2 h under a low transmembrane pressure of 0.4 MPa. The flux recovery ratio of the nanofiltration membrane was 63% higher than the PES support membrane, indicating an improvement in fouling resistance.

Polyethersulfone (PES)-based mixed matrix nanofiltration membrane was developed by blending with partially reduced graphene oxide (rGO)/TiO 2 nanocomposite. The effect of rGO/TiO 2 contents on the morphology and performance of the prepared membranes was investigated by scanning electron microscopy (SEM), energy dispersive X-ray (EDX), atomic force microscopy (AFM) and water contact angle analysis. The blended membranes displayed improved water permeability and fouling resistance compared to the bare PES. When the content of rGO/TiO 2 was 0.15 wt.%, the water flux reached a maximum value (45.0 kg/m 2 h) nearly twice of that of the bare PES membrane (23.1 kg/m 2 h). Fouling resistance of the membranes studied by bovine serum albumin (BSA) solution filtration showed that 0.1 wt.% rGO/TiO 2 membrane had the best antifouling property. Nanofiltration performance of the prepared membranes was evaluated by rejection of three organic dyes with different molecular weights (i.e. C. I. Reactive Green 19, C. I. Direct Yellow 12 and C. I. Reactive Blue 21). The rGO/TiO 2 /PES membranes showed better dye removal performance than the bare PES. Compared with TiO 2 /PES and GO/PES membranes, rGO/TiO 2 /PES membranes presented the best water permeation rate, antifouling ability and dye rejection.

A modified thin film composite nanofiltration (TFC/NF) membrane was prepared by interfacial polymerization between piperazine and trimesoyl chloride monomers and NH 2 functionalized multiwalled carbon nanotube (NH 2 -MWCNT) as a hydrophilic modifier. The surface morphology and hydrophilicity of the prepared NF membranes were studied by scanning electron microscopy (SEM) and water contact angle measurements, respectively. These analyses showed the higher hydrophilicity and the smoother surface of the modified membranes. Also, the separation performance of the membranes was investigated using 2000 mg/L of Na 2 SO 4 and NaCl solutions tested by cross-flow filtration system. The NF membrane modified with 0.005 wt% NH 2 -MWCNT presented the best separation performance, including 36.71 and 95.72% rejection of Na 2 SO 4 and NaCl salts, respectively. The fouling resistance of the membranes was also studied using bovine serum albumin (BSA) protein as a model fouling agent, based on the water flux decline during the filtration process. Results showed that the membranes containing NH 2 -MWCNT in the polyamide layer have improved fouling resistance compared to the unmodified NF.

A novel polyvinylidene fluoride (PVDF) ultrafiltration membrane blended with different concentrations of SAPO-34 nanoporous zeolite was fabricated by the non-solvent induced phase inversion method. The prepared blended membranes were characterized by scanning electron microscopy (SEM), water contact angle, porosity, energy dispersive X-ray (EDX), and permeation analyses as well as fouling and rejection tests. The SEM images of the membranes showed an asymmetric structure possessing a dense top-layer and a combination of spongy and finger-like porous sub-layer. The modified PVDF membranes had lower water contact angle, higher hydrophilicity and water flux due to the presence of hydrophilic SAPO-34 zeolite in the polymer medium. All of the nanocomposite membranes showed higher flux recovery ratio ( FRR (%)) compared to the unfilled PVDF membrane. The membrane containing 0.5 wt% SAPO-34 had the best antifouling performance ( FRR = 89.4%) with a bovine serum albumin (BSA) rejection value more than 99%.

In this research, the PVDF-based nanocomposite membranes modified with ZIF-8 nanocrystals were prepared with various casting solvents containing, DMSO, NMP, DMF and DMAc. The SEM, EDX and AFM analyses were applied to study morphology, distribution of the ZIF-8 in the matrix of the polymer, and surface roughness characteristic of the mixed matrix membranes, respectively. The impact of the solvent type on the structure and filtration efficiency of the resulting membranes was studied by considering the thermodynamic and kinetic factors of the membrane formation. A significant correlation was found between the diffusion rates of the solvent/non-solvent and the sub-layer structure of the membranes. Membranes cast with DMAc and DMF solvents (with relatively high diffusion rates) presented a bigger number of the finger-like cavities with a smaller size compared with membranes prepared by DMSO and NMP with lower diffusion rates. Blending of the ZIF-8 nanoparticles within the membrane matrix with a proper concentration (up to 0.2 wt%) resulted in an increase in the size of the finger-like cavities, lead to increase in the permeability of the resulting membranes. With increasing the ZIF-8 content to 0.5 and 1 wt%, the finger-like pores turned to sponge-like pores. The pure water permeation of the unmodified membranes cast with DMSO, NMP, DMAc and DMF was 258.64, 179.52 156.65 and 10.52 L/m2h, respectively, which was in good agreement with the observed trend for porosity and surface hydrophilicity of the membranes.

In this research, bulk MoS2 was exfoliated and functionalized using ultrasonic irradiation. The prepared nanolayered MoS2 was characterized using scanning electron microscopy (SEM), UV-Vis absorption, Fourier transform infrared spectroscopy (FT-IR), and X-ray diffraction (XRD) analyses. The nanolayered MoS2 was applied as a hydrophilic additive for modification of polyethersulfone (PES) ultrafiltration membrane. The MoS2/PES nanocomposite membranes with various contents of MoS2 were fabricated using non-solvent induced phase-inversion method. Finger-like morphology was observed for fabricated membranes in cross-section SEM images. According to the results of the atomic force microscopy (AFM) analysis, the optimum nanocomposite membrane represented highest average surface roughness and consequently highest efficient area for filtration compared with other nanocomposite membranes. The contact angle analysis confirmed hydrophilicity improvement of PES membrane by embedding nanolayered MoS2. The performance of the PES membrane was optimized in the presence of appropriate content of the hydrophilic nanolayered MoS2 (0.2 wt%). The pure water flux and flux recovery ratio of the 0.2 wt% MoS2/PES nanocomposite membrane were respectively 45% and 30% higher than that of the bare PES membrane. Finally, the optimized nanocomposite membrane was used for the treatment of oil refinery wastewater. The flux of the bare and optimum nanocomposite membrane was reached to 58% and 73% of their initial flux after160 min of filtration. This confirmed better fouling resistance performance of optimum nanocomposite membrane compared with the bare one. The COD and the turbidity of the wastewater were decreased from 240 mg/L and 12.2 NTU to 40.8 mg/L and 2.1 NTU, respectively, after 160 min filtration by optimum nanocomposite membrane.

Water purification is the collective name for a group of processes that make water more suitable for drinking, medical use, industrial use, and so on. A water purification process is designed to remove or reduce existing water contaminants to the point where the water is fit for use. In the last few years, innovative methods such as nanotechnology have been studied to develop water purification technologies. Graphene is a two-dimensional mesh of carbon atoms arranged in the form of a honeycomb lattice. It has earned the title, “miracle material,” thanks to a startlingly large collection of beneficial properties. It is thought that graphene could revolutionize the whole industry, as researchers work on many different kinds of graphene-based materials, each one with unique qualities and designation. The present chapter surveys and reviews the recent research and published literature on the graphene-based materials for water purification. The main methods discussed are adsorption, photocatalysis, membrane filtration, and electrochemical water purification.

A thin film nanocomposite nanofiltration (TFN–NF) membrane was prepared by interfacial polymerization between piperazine and trimesoyl chloride monomers and partially reduced graphene oxide (rGO)/TiO2 nanocomposite as a hydrophilic modifier. The surface properties of the prepared NF membranes were characterized by scanning electron microscopy (SEM), atomic force microscopy (AFM) and water contact angle measurements. These analyses confirmed the improved hydrophilicity and the smoother surface of the modified membranes. Furthermore, the separation performance of the membranes was evaluated using 2000 mg/L of Na2SO4 and NaCl solutions tested by cross-flow filtration system. TFN membrane containing 0.005 wt.% rGO/TiO2 presented the optimum separation performance, including 60.6 L/m2 h water flux and 93.57% and 36.61% salt rejection of Na2SO4 and NaCl solutions, respectively. The fouling resistance of the membranes was also studied using bovine serum albumin (BSA) protein as a model fouling agent, based on the water flux decline during the filtration process. Results showed that decoration of TiO2 nanoparticles onto GO nanosheets had dual effects on the TiO2 incorporation into the cross-linked active layer of NF membrane, thereby improved the fouling resistance of these membranes.

A novel thin film nanocomposite reverse osmosis (TFN-RO) membrane was prepared by interfacial polymerization of m-phenylenediamine (MPD) and trimesoyl chloride (TMC) monomers and embedding reduced graphene oxide (rGO)/TiO 2 nanocomposite in its polyamide layer. The rGO/TiO 2 nanocomposite was added to the MPD solution with aim of improving RO performance, enhancing antifouling property and increasing chlorine resistance. Surface scanning electron microscopy (SEM) images show that all of the membranes have a rough surface with a layer of “ridge-and-valley” structure that is typical morphology of MPD/TMC polyamide membranes. The contact angle analysis showed that hydrophilicity of the membranes was improved by increasing the concentration of rGO/TiO 2 due to the presence of various hydrophilic and negatively charged functional groups on the rGO/TiO 2 nanocomposite. The superior performance of the rGO/TiO 2 /RO membrane was observed in the case of 0.02 wt% rGO/TiO 2 with water flux of 51.3 L/m 2 h and salt rejection of 99.45%. Antifouling ability of the membranes studied by bovine serum albumin (BSA) solution filtration showed that 0.02 wt% rGO/TiO 2 /RO membrane had the best antifouling property. Also, after the chlorination tests, the salt rejection of the bare RO membrane decreased by 30%, while this value was only 3% for 0.02 wt% rGO/TiO 2 /RO membrane which confirmed its great chlorine resistance.

This chapter surveys the recent published literatures and current studies on the carbon-based nanomaterial embedded membranes and their applications in the desalination process. Using nanomaterials in the preparation of membrane has not only demonstrated excellent antifouling resistance, but also possibly overcome the trade-off effect between water permeability and solute selectivity. Nanomaterials affect the permeability, selectivity, hydrophilicity, conductivity, mechanical strength, thermal stability, and the antiviral and antibacterial properties of polymeric membranes. This chapter includes an introduction to carbon-based nanomaterials, fabrication of nanocomposite desalination membranes, and their properties with respect to desalination. This involves different membrane processes, and opportunities and challenges of those materials in desalination applications.

A partially reduced graphene oxide (rGO)/TiO2 nanocomposite with five different molar ratios (rGO/TiO2: 3/97, 30/70, 50/50, 70/30 and 90/10) were synthesized and characterized using X-ray diffraction and scanning electron microscopy (SEM) techniques. The polyvinylidene fluoride (PVDF) mixed matrix membranes containing 0.05 wt.% of the nanocomposites were prepared by phase inversion method. The effect of rGO/TiO2 additive on the morphology and performance of prepared blended membranes was studied by atomic force microscopy (AFM), SEM, energy dispersive X-ray (EDX), FTIR, water contact angle, porosity and permeation measurements, rejection tests and antifouling parameters. The SEM images revealed finger-like structure of the membranes and EDX analysis confirmed well distribution of rGO/TiO2 nanocomposite in the polymer matrix. The rGO/TiO2/PVDF membranes showed enhanced hydrophilicity, higher pure water flux and flux recovery ratio compared to the bare PVDF. A comparison of pure water flux of TiO2 and rGO/TiO2 containing membranes showed that dispersion of inorganic TiO2 nanoparticles on the GO surface decreased the aggregation of the nanoparticles and improved the characteristics of the resulted mixed matrix membrane. The blended membrane containing 0.05 wt.% rGO/TiO2 nanocomposite with GO to TiO2 ratio of 70/30 showed improved permeability and antifouling performance.

Pure and Eu-doped ZnO nanostructures with different amounts of Eu were synthesized using a simple sonochemical method. The as-synthesized samples were characterized by X-ray diffraction, scanning electron microscopy, UV–Vis spectroscopy, Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy. The photocatalytic activity of as-prepared Eu-doped ZnO was investigated based on the decolorization of Acid Red 17 (AR17) under visible light irradiation. The decolorization efficiency was found to be 25.2%, 55.6%, 63.1% and 30.3% for undoped, 1% Eu-ZnO, 3% Eu-ZnO and 5% Eu-ZnO, respectively. Using 3% Eu-doped ZnO nanoparticles, the decolorization efficiency reached 100% by adding 0.1 mM S 2 O 8 2− . Response surface methodology based on five-level central composite design was applied to model and optimize the decolorization of AR17 over 3% Eu-doped ZnO/S 2 O 8 2− . Accordingly, the value of correlation coefficients ( R 2 = 0.970 and adjusted- R 2 = 0.935) obtained from analysis of variance confirmed the adequacy of fitted model. The maximum decolorization efficiency of 99% was achieved at an initial dye concentration of 5 mg/L, catalyst dosage of 1.25 g/L, S 2 O 8 2− concentration of 0.25 mM and reaction time of 150 min. The decolorization efficiency decreased only 7% after 4 repeated runs.

In this study, Yb-doped ZnSe nanoparticles were synthesized by co-reduction method at 150 degrees C and pH = 12 for 24 h. The obtained materials were characterized by X-ray diffraction (XRD), UV-Vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Powder XRD patterns indicated that the Yb(x)Zn(1-x)Se crystals (x = 0.00-0.10) are isostructural with ZnSe. SEM and TEM images confirmed doping of Yb3+ into the lattice of ZnSe nanoparticles. The UV-Vis diffuse reflectance characteristics of the Yb-doped ZnSe samples were quite similar to that of the undoped sample and showed a strong photoabsorption at visible light range. The electrical conductivity of Yb-doped ZnSe nanomaterials was higher than pure ZnSe at room temperature, and increased with temperature. The photocatalytic activity of synthesized nanoparticles was investigated by the degradation of Orange II solution under visible light irradiation. It was observed that the color removal efficiency of Yb-doped ZnSe catalyst was much higher than that of pure ZnSe (26.28 and 77.10% after 120 min of treatment for ZnSe and Yb(0.06)Zn(0.94)Se, respectively). The results demonstrated the good photocatalytic ability of synthesized nanoparticles under visible light. Also, it was revealed that the decolorization efficiency of Orange II over Yb-doped ZnSe increased with increasing Yb loading up to 6 mol% and then decreased.

A novel polyvinylidene fluoride (PVDF) mixed matrix ultrafiltration membrane containing reduced graphene oxide/titanium dioxide (rGO/TiO2) nanocomposite was prepared by phase inversion method. The synthesized rGO/TiO2 was characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and scanning electron microscopy (SEM) techniques. The prepared rGO/TiO2 blended PVDF membranes were characterized by atomic force microscopy, SEM, water contact angle, porosity, permeation measurements, and rejection tests. Due to the high hydrophilicity of the rGO/TiO2 nanocomposite, the rGO/TiO2/PVDF membranes were more hydrophilic and had higher pure water flux and flux recovery ratio than the bare PVDF. The blended membranes showed remarkably good properties and performance when the rGO/TiO2 content of 0.05 wt % was added to the casting solution. The pure water flux of the 0.05 wt % rGO/TiO2 blended membrane was increased by 54.9% compared with the bare PVDF membrane. The antifouling study of the membranes ...

In this paper, degradation of a mixture of three azo dyes was studied by the photo-assisted electrochemical process using an O2-diffusion cathode containing carbon nanotubes and boron-doped diamond (BDD) anode. The concentration of three textile dyes (C.I. Acid Orange 8 (AO8), C.I. Acid Orange 10 (AO10), and C.I. Acid Orange 12 (AO12)) was determined simultaneously despite the severe overlap of their spectra. For this purpose, partial least square (PLS), as a multivariate calibration method, was utilized based on recording UV–Vis spectra during the decolorization process. Moreover, the central composite design was used for the modeling of photo-assisted electrochemical decolorization of the aqueous solutions containing three dyes. The investigated parameters were the initial concentration of three dyes, applied current and reaction time. Analysis of variance (ANOVA) revealed that the obtained regression models match the experimental results well with R (Khataee et al. 2010, Clean-Soil Air Water 38 (1):96–103, 2010) of 0.972, 0.971, and 0.957 for AO8, AO10, and AO12, respectively. Three-dimensional surface and contour plots were applied to describe the relation between experimental conditions and the observed response. The results of TOC analysis confirmed good ability of proposed photo-assisted electrochemical process for degradation and mineralization of textile industry wastewater.

The zeolitic imidazolate framework-8 (ZIF-8) nanoparticles were synthesized at two different sizes of 80–100 nm (ZIF-8 (Z1)) and 60–70 nm (ZIF-8 (Z2)) and characterized with scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray powder diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and Brunauer–Emmett–Teller (BET) analyses. The synthesized ZIF-8 nanoparticles were used for modification of polyvinylidene fluoride (PVDF) ultrafiltration membranes prepared by the phase inversion technique. The SEM and atomic force microscopy (AFM) analyses were used to monitor the changes in the morphology and surface properties of the bare and ZIF-8 modified membranes. The results of AFM analysis revealed the decrease in the surface smoothness of the modified membranes. The ZIF-8/PVDF mixed matrix membranes presented higher water flux than the bare PVDF membranes owing to their higher porosity and suitable pore size of the ZIF-8 nanoparticles. By addition of 0.1 wt% of ZIF-8 (Z1) and 0.2 wt% ZIF-8 (Z2) nanoparticles, the modified membranes displayed water flux of 310 and 275 L/m2h, respectively, with 98 and 76% increase compared with the unmodified PVDF membrane. The results indicated that the membranes modified with larger ZIF-8 particles (80–100 nm) showed higher permeability and flux recovery ratio (FRR %) than those with smaller particles (60–70 nm).

Membrane bioreactors (MBRs) have received increasing attention in the field of wastewater treatment in recent years. However, membrane fouling is the main problem of MBRs, limiting their widespread and large applications. Membrane cleaning methods can be mainly classified into four types including chemical, physical, physico-chemical and biological clean the fouled membrane. In recent years, ultrasonication has been reported as a promising cleaning technique for the membranes fouled in MBRs. Ultrasonic irradiation can clean the fouled membrane by creating important physical phenomena including microjets, microstreams and shock waves. Moreover, the ultrasonic method can be combined with other cleaning methods e.g. chemical cleaning and backwashing in order to improve the cleaning efficiency. It should be noted that the application of ultrasonic in the MBR system is not limited to the cleaning of membrane. The pretreatment of the wastewater by ultrasonic irradiation or ultrasound coupled with other methods, e.g. ozonation, prior to MBR system, can decrease the organic loading of the wastewater and subsequently postpone the fouling of the membrane. This paper critically reviews the recent advances in the applications of ultrasound in MBR systems. Emerging issues associated with application of on-line ultrasound and also hybrid on-line ultrasound for controlling the membrane fouling in MBR systems are critically reviewed. Moreover, application of the ultrasound in ex-situ form for cleaning the fouled membranes and pretreatment of wastewater prior to the MBR system is discussed.

We investigated the treatment of a mixture of three reactive textile dyes (C. I. Reactive Red 195, C. I. Reactive Yellow 84 and C. I. Reactive Blue 69) by electro-Fenton (EF) process using carbon paper cathode modified with carbon nanotubes (CNTs). To study the degradation of mixture of three dyes, a rapid analytical methodology based on recording UV-Vis spectra during the EF process and the data treatment using partial least square (PLS) as a multivariate calibration method was developed. The three reactive dyes were quantified simultaneously despite the overlap of their spectra. Central composite design was used in the modeling and optimization of the electrochemical decolorization process. The independent variables for modeling were initial concentration of three dyes, applied current in the electrolysis system, and reaction time. Results indicated that the optimum applied current value was about 400mA for the EF process. Analysis of variance (ANOVA) showed that predicted responses by CCD match the experimental values logically with the amount of R2 more than 0.92.

Dy-doped ZnO nanoparticles were synthesized with a sonochemical method. X-ray diffraction, inductively coupled plasma, Fourier transform infrared spectroscopy, UV–vis diffuse reflectance spectroscopy, and scanning electron microscopy analyses confirmed the successfully synthesis and nanometric diameter of the samples. Dy-doped ZnO nanoparticles were used for photocatalytic decolorization of C. I. Acid Red 17 solution under visible light irradiation. Among different amounts of dopant agent, 3% Dy-doped ZnO nanoparticles indicated the highest decolorization. Decolorization efficiency increased from 14.3 to 57.0% with an increase in catalyst dosage from 0.25 to 1 g/L, while further increment in the catalyst dosage up to 2 g/L caused an obvious decrease in decolorization efficiency. The addition of 0.1 mM peroxydisulfate (S2O82–) resulted in a decolorization efficiency of nearly 100% after irradiation for 180 min. The trend of inhibitory effect in the presence of different radical scavengers was Cl– > C2H5OH ...

In the present study, self-cleaning and mechanical properties of white Portland cement by addition of commercial available TiO2 nanoparticles with the average particle size of 80 nm were investigated. X-ray diffraction (XRD), transmission electron microscopy (TEM) and BET were used to characterize TiO2 nanoparticles. For determination of self-cleaning properties of TiO2-modified white cement, colorimetric tests in decolorization of C.I. Basic Red 46 (BR46) in comparison to unmodified cement samples was applied. The results indicated that with increasing the amount of TiO2 nanoparticles in modified cement, self-cleaning property of the samples increased. The mechanical properties of TiO2-modified and unmodified cement samples, such as time of setting of hydraulic cement, compressive strength of hydraulic cement mortar and flexural strength of hydraulic cement mortar were examined. The results indicated that addition of TiO2 nanoparticles up to maximum replacement level of 1.0% improved compressive and flexural strength and decreased its setting time.

In the present study, Nd3+-doped ZnSe nanoparticles with variable Nd contents were successfully synthesized via a hydrothermal process using Neodymium (III) chloride hexahydrate as the doping source. X-ray diffraction, UV–Vis diffuse reflectance spectroscopy (DRS), scanning electron microscopy and transmission electron microscopy were used for characterization of the synthesized nanoparticles. It was confirmed by the DRS analysis that both of the undoped and Nd-doped ZnSe samples had significant optical absorption in the visible light range. The photocatalytic performance of as-synthesized nanoparticles was investigated towards the decolorization of C. I. Acid Orange 7 solution under visible light irradiation. Results indicated that the loading of Nd dopant into ZnSe nanoparticles significantly enhanced the photocatalytic activity of pure ZnSe with increasing Nd loading up to 6 mol% (color removal efficiency of 24.31 % for ZnSe and 84.20 % for Nd0.06Zn0.94Se after 120 min of treatment) and then the photocatalytic activity began to decrease.

In this paper, the efficiency of photoelectro-Fenton (PEF) combined with photocatalytic process was studied for decolorization of C.I. Acid Yellow 36 (AY36) as a model textile dye. The investigated photocatalyst was TiO 2 nanoparticles (Degussa P25) immobilized on glass plates. The efficiency of three cathode materials (i.e. bare graphite, activated carbon immobilized onto graphite surface (AC/graphite) and carbon nanotubes immobilized onto graphite surface (CNT/graphite)) was investigated for H 2 O 2 electrogeneration and dye removal. The CNT/graphite electrode fed with air had the best efficiency for H 2 O 2 production and decolorization of AY36 solution. A comparison of electro-Fenton (EF), UV/TiO 2 , PEF, photolysis and PEF/TiO 2 processes for dye removal was performed. Results showed that decolorization followed the decreasing order: PEF/TiO 2 > PEF > EF > UV/TiO 2 > photolysis. Central composite design (CCD) was employed to model and optimize the decolorization of dye solution using combined process. The variables for CCD optimization were initial concentration of Fe (III) and dye, reaction time and applied current. Analysis of variance (ANOVA) showed high coefficient of determination value ( R 2 = 0.9867 and adjusted- R 2 = 0.9751). The degradation pathway of AY36 was proposed based on the identified compounds by GC–Mass technique. The unit energy demand (UED) and operating cost for photoelectrocatalytic process was evaluated.

In this paper simultaneous photooxidation of three textile dyes (CI Basic Red 46 (BR46), Malachite Green (MG) and CI Basic Blue 3 (BB3)) by UV/H2O2 process is reported. A rapid analytical methodology based on recording UV-Vis spectra during the photooxidative decolourization process and the data treatment using multivariate curve resolution with alternating least squares (MCR-ALS) was developed. The three textile dyes were quantified simultaneously despite the overlap of their spectra. Also, the central composite design was applied for optimization of the photooxidative decolourization of the solution containing three dyes using the UV/H2O2 process. The investigated factors (variables) were the reaction time, initial concentration of the three dyes and initial concentration of H2O2. The optimum initial concentration of the three dyes, H2O2 initial concentration and reaction time were found to be 4 mg/L, 48 mg/L and 30 min, respectively. The photodegradation products of three dyes were identified by the GC-MS technique.

The electrochemical treatment of dye solution containing C.I. Direct Red 23 (DR23) has been studied under recirculation mode with an UV irradiation of 15 W. Decolorization experiments were performed in the presence of sulfate electrolyte media at pH 3.0 with carbon nanotube-polytetrafluoroethylene (CNT-PTFE) electrode as cathode. A comparison of electro-Fenton (EF) and photoelectro-Fenton (PEF) processes was carried out for decolorization of DR23 solution. Color removal efficiency was 66.22% and 94.29% for EF and PEF processes after 60 min treatment of 30 mg/L DR23, respectively. The effect of operational parameters on the PEF process such as applied current, initial pH, flow rate, initial Fe3+ concentration and initial dye concentration was investigated. Results indicated that the optimal conditions for decolorization process were applied current of 0.2 A, flow rate of 10 L/h, pH = 3, initial Fe3+ concentration of 0.05 mM and initial dye concentration of 10 mg/L. An artificial neural network (ANN) model was developed to predict the decolorization of DR23 solution, which provided reasonable predictive performance (R2 = 0.958). © 2012 American Institute of Chemical Engineers Environ Prog, 32: 557–563, 2013

In this paper, we studied treatment of mixture of three azo dyes using homogeneous photoelectro-Fenton (PEF) combined with heterogeneous photocatalytic process (UV/TiO 2 ). Carbon nanotube immobilized onto graphite plate (CNT/graphite) electrode was used as cathode. The investigated photocatalyst was TiO 2 nanoparticles (Degussa P25) immobilized on glass plates. A rapid analytical methodology based on recording UV–Vis spectra during the photoelectro-Fenton/photocatalytic decolorization process and the data treatment using multivariate calibration methods such as partial least square (PLS) was developed. The three textile dyes (C.I. Acid Yellow 36 (AY36), C.I. Acid Red 14 (AR14) and C.I. Basic Yellow 28 (BY28)) were quantified simultaneously despite the overlap of their spectra. Also, the central composite design has been employed to the optimization of photoelectro-Fenton/photocatalytic decolorization of the dye solution containing three dyes using combined process. The factors (variables) investigated were the initial concentration of three dyes, initial amount of Fe 3+ and reaction time. Results indicated that the optimum Fe 3+ concentration was 0.15 mM for decolorization process. Analysis of variance (ANOVA) showed that predicted values match the experimental values reasonably well with R 2 of 0.965, 0.943 and 0.947 for AY36, AR14 and BY28, respectively. Three-dimensional surface plots have been used to present the relation between independent variables and dependent variable (response).

Three cathode materials (i.e. bare graphite, activated carbon immobilized onto graphite surface (AC/graphite) and carbon nanotubes immobilized onto graphite surface (CNTs/graphite)) were investigated for electrochemical generation of hydrogen peroxide. The amount of electrogenerated H 2 O 2 using CNTs/graphite fed with air was nearly three times higher than that of AC/graphite and seven times higher than that of bare graphite. The effect of some operational parameters such as applied current, supporting electrolyte concentration, air flow rate and pH on the generation of H 2 O 2 was investigated. Results indicated that the optimal conditions for H 2 O 2 generation were applied current of 100 mA (2.5 mA/cm 2 ), air flow rate of 2.5 L/min, and pH = 3. After eight times reuse, electrochemical generated hydrogen peroxide concentration dropped from 118.65 μM to 114.63 μM, indicating a decay of 3.6%. This fact indicates that the present system can be useful for the in situ electrochemical generation of hydrogen peroxide.

Pure and erbium (Er)-doped ZnO samples were synthesized through a sonochemical method and characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), UV–Vis spectroscopy, and X-ray photoelectron spectroscopy (XPS) analysis. The synthesized samples were used as a catalyst for the sonocatalytic decolorization of Reactive Orange 29 (RO29) as a model organic pollutant. The decolorization efficiency was 63%, 68%, 88%, and 75% for undoped, 2%, 4%, and 6% Er-doped ZnO, respectively. The effect of different experimental parameters including catalyst content, dye concentration and ultrasound power was investigated on the sonocatalytic decolorization of RO29. Among several radical scavengers (i.e. chloride, carbonate and sulfate anions and t-butanol), the chloride anion showed the most inhibitive effect on the sonocatalysis performance. Improvement of the sonocatalytic process by K 2 S 2 O 8 and H 2 O 2 enhancers was also studied. The reusability of the synthesized sonocatalyst was evaluated in several consecutive runs, and a decline of only 4% was observed in the process performance after five runs. The intermediates produced during the degradation of RO29 were identified by GC–MS analysis.